On March 12, 2004, about 0930 eastern standard time, a Robinson R22, N4370D, registered to and operated by Collective Helicopters Corporation, as a Title 14 CFR Part 91 instructional flight, rolled over while practicing maneuvers at the Keystone Airpark, Keystone Heights, Florida. Visual meteorological conditions prevailed and no flight plan was filed. The instructor-rated pilot and student pilot received no injuries, and the helicopter incurred substantial damage. The flight originated from Keystone Airpark, Florida earlier that day. The certified flight instructor stated that he had his student complete several steep turn maneuvers earlier in the practice session and decided to let him perform one more before returning back to the hangar. On the last steep turn the student lost more altitude then on previous maneuvers. According to the instructor he took over the controls; however, the helicopter touched down right skid lower than the left with forward left lateral movement resulting in the helicopter rolling over on to the ground. The flight instructor stated there were no mechanical failures or malfunctions to the helicopter or any of its systems prior to the accident.